Saboted munition with a movable fin group

ABSTRACT

An armor piercing convertible fin saboted round for a machine gun includes penetrator on which a fin group is mounted so that the penetrator can extend into a prelaunch sabot with the fin group arranged around the penetrator. The fin group advantageously carries a pin which engages in an elongated groove defined on the penetrator and permits the fin group to slide along the body of the penetrator during launch so that it may move from a forward position adjacent the tip of the penetrator rearwardly during launch to an end position in which it is engaged adjacent the end of the penetrator and stabilizes the penetrator during flight.

GOVERNMENTAL INTEREST

The invention described herein may be made or used by or for theGovernment for governmental purposes without payment to me of anyroyalties thereon.

FIELD AND BACKGROUND OF THE INVENTION

This invention relates in general to saboted rounds of ammunition and inparticular to a new and useful saboted round for a machine gun whichincludes a fin group which rides on a penetrator. It may move from aforward position of prelaunch in which the penetrator is arranged withina sabot to a post launch configuration in which the stabilizing fingroup is movable back along the penetrator to a rear position in whichit stabilizes the penetrator.

The invention is designed to insure that a saboted sub-calibre machinegun ammunition is improved in its performance by the use of a movablefin group construction which is disposed around a penetrator. Increasedvelocity and accuracy are desirable features in small caliberprojectiles. In any instance there is a transient instability during aflight of the projectile during launching. This imposes a largeperformance penalty on the projectile. Such instabilities are aggravatedin sub-calibre fin stabilized projectiles by collisions betweendiscarded sabot and the fins of the projectile.

SUMMARY OF THE INVENTION

In accordance with the invention the projectile is provided with a finwhich rides on a penetrator at the forward end when it is in a prelauncharrangement within a sabot. In accordance with the invention the fingroup is arranged on the penetrator so that it rides on the body of thepenetrator up to the point of sabot discard.

In an arrangement of the invention a sliding fin group is positioned onthe penetrator in front of the sabot. When the sabot leaves thepenetrator the fin group is free to move to the rear of the penetratorunder the influence of aerodynamic drag forces. With the inventivearrangement the fin group is arranged on the penetrator at a location inwhich it extends out of the sabot and is thus out of the sabot discardpath at all times.

In accordance with the invention a fin group transfer failure due tococking and sticking is not possible. This is overcome by controllingtolerances between the fin group which is arranged on the penetrator andthe penetrator outside diameter. In some instances it is also desirableto use a dry lubricating process on the penetrator to effect the desiredmovement between the fin group and the penetrator. A further alternativeis the use of a nylon liner or a contoured spring steel buffer for thefin group.

With the inventive arrangement it is possible to launch the penetratorfrom the sabot in a manner which does not adversely influence thestability of the penetrator.

An object of the invention is to provide an improved arrangement for themounting of a fin group on a penetrator carried in a sabot so that thereis no substantial disturbance of the flight of the penetrator and itsstabilization is insured.

A further object of the invention is to provide an arrangement of a fingroup in respect to a penetrator of saboted sub-calibre machine gunammunition which is simple in design, rugged in construction andeconomical to manufacture.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of this disclosure. For a better understanding of the invention,its operating advantages and specific objects obtained by its uses,reference is made to the accompanying drawings and descriptive matter inwhich preferred embodiments of the invention are illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS

In the Drawings:

FIG. 1 is a sectional view of a saboted ammunition constructed inaccordance with the invention;

FIG. 2 is a view similar to FIG. 1 indicating the mid-launch of apenetrator of saboted ammunition shown in FIG. 1; and

FIG. 3 is view showing the post launch arrangement of the sabotedammunition.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawings in particular, the invention embodied thereincomprises an armor-piercing convertible fin saboted round for a fiftycaliber machine gun generally designated 50. The round 50 includes asabot or launching tube 52 in which is positioned a penetrator 54 havinga forward tip 54a and a trailing end 54b. In FIG. 1 the trailing end 54bis located in the sabot 52 and the tip 54a extends out of the sabot. Abase plate 56 is located inside the sabot 52.

In accordance with the invention a fin group 58 includes a collar 58awhich extends around the penetrator 54 and carries a plurality ofcircumferentially spaced radially extending fins 58b.

In the initial pre-launch position shown in FIG. 1 the fins 58 lieadjacent the outer edge 52a of the sabot 52. In accordance with afeature of the invention guide means are defined between the fin group58 and the penetrator 54 and in the embodiment illustrated they comprisea pin 60 which rides in a longitudinally extending groove 62 which isdefined on the penetrator 54.

Immediately after launch, the pin 60 rides in the groove 62 due to thedrag forces acting on the fin group 58 it moves backwardly along thepenetrator 54 from its foremost position and finally ends up in atrailing position shown in FIG. 3 in which the pin 60 engages at the endof the groove 62 and stabilizes the penetrator 54 in a post-launchposition. The period of flight from the initial prelaunch position tothe post launch position of FIG. 3 can be estimated to about 2 to 3milliseconds duration from photographic records of saboted rounds whichare currently under development. During the first millisecond of flightthe sabot is discarded. In the remaining two milliseconds the projectiletravels through a region of gas discharge from the muzzle that can becharacterized as a reverse flow with respect to the projectile. In sucha flow the fins will be in a proper position for stabilizing the roundor penetrator 54. As reverse flow dissipates and is overcome by forwardflow, drag forces push the fin group to the rear end of the projectilestabilizing it in the forward flow. Calculation shows that the fin groupshould travel to the rear of the projectile in about 62.5 microseconds.A transition of such a brief duration virtually eliminates thepossibility of instability due to fin transition. In order to insurethat the fin group 58 does not override the base the fin group is guidedby the pin 60 in the groove 62 and will stop at the rear end of travelof the groove. Shear problems can be overcome by the sizing of the pinand the groove.

In some instances there is a coupling of the sabot 52 and the penetratorprojectile 54. Thrust washers used in such a construction will be sizedto provide the desired degree of friction reduction. Additional fractionreduction will be achieved through the use of a Teflon coating for thepenetrator bearing surfaces.

While a specific embodiment of the invention has been shown anddescribed in detail to illustrate the application of the principles ofthe invention, it will be understood that the invention may be embodiedotherwise without departing from such principles.

What is claimed is:
 1. A saboted round for a machine gun, comprising asabot, a penetrator having a body portion located within said sabot andhaving a tip extending out of the end thereof, and a fin group carriedon said penetrator and being movable along the surface of saidpenetrator upon discharge from said sabot to a position at the rear endof said penetrator.
 2. A machine gun round according to claim 1, whereinsaid fin group includes a plurality of radially extending fins mountedon said penetrator around the circumference thereof and including meansdefining a guide for said fin group along the length of said penetratorfor stopping said fin group adjacent the rear of said penetrator.
 3. Amethod of firing a saboted machine gun ammunition, using a fin assemblyhaving a generally cylindrical portion and fins extending substantiallyradially from the cylindrical portion in association with a penetrator,the penetrator having a forward tip and an opposite trailing end;comprising placing the penetrator in a sabot so arranged that theforward tip and a length of the penetrator extends out of the sabot, andafter firing, permitting the fin assembly to move down the penetrator asit exits from the sabot so that it moves to position close to thetrailing end.
 4. Ammunition comprising a substantially cylindricalhollow sabot having a closed end and an opposite open end, a penetratorhaving an inner nd close to said closed end and an opposite tip endextending out of said opposite open end, a fin member engaged on theexterior of said penetrator over a portion thereof extending out of saidopposite open end and means connected between said penetrator and saidfin member permitting movement of said penetrator and said fin memberrelatively so as to position said fin member close to said inner endimmediately upon exit of said penetrator from said sabot during firing.